A measuring method of the single-phase AC frequency, phase, and reactive power based on the Hilbert filtering

This paper presents a novel measuring method based on the Hilbert filtering for the digital monitoring of the single-phase ac frequency, phase, and reactive power. According to this method, the sampled voltage signal passes a pair of the Hilbert filters. Then, the ac frequency and phase can be obtained by the phase detection and the phase-locked loop algorithm. Additionally, the sampled current signal also makes its phase shift by the other Hilbert filter. The current output is multiplied by the one of the phase-shifted voltage signals, and the reactive power is acquired from the de component of the product. Because a type of infinite impulse response (HR) Hilbert filters with low-order and small phase-shift error is adopted, this measuring method cannot only obtain fast and accurate digital monitoring results but also be easily realized with the DSP or other microprocessor programming codes. This method has been successfully applied in the design of a digital multifunctional power instrument.